Governor for gas turbine engines including inlet condition bias during steady state operation



June 11, 1963 A. A. KUZMITZ 3,092,966

GovERNoR FOR GAS TURBINE ENGINEs INCLUDING INLET CONDITION BIAS DURING STEADY STATE OPERATION Original Filed March 1, 1954 2 Sheets-Sheet 1 0 g T1 .4- }t 055/250 414x. 7%5 727W? 0 max. AZZOW 525w w/m Ta 5. Pa COMPE/V. g 225 70, 3 k or. 4mm mrv re 230 ca/vPiM a/vzr 60F .907: COMP/Q was? 727%? +2baF E Q Max. 51v .5 55; {,2 Anal/$7M xv?" mx. E 2 (s w I i /o p/zarj fl :7? 44 15 90 INVENTOR.

June 11, 1963 A. A. KUZMITZ 3,092,966

GOVERNOR FOR GAS TURBINE ENGINES INCLUDING INLET CONDITION BIAS DURING STEADY STATE OPERATION Original Filed March 1, 1954 v 2 Sheets-Sheet 2 N65 pVA 59 CMP/FJ/VLET COMP/95550,? 9/5 CV/AFGE PPE'SSMPE A! MIA .5

IN V EN TOR.

yfl/m ATTO/FA/f) United States Patent 3,02,966 GDVERNOR FOR GAS TURBINE ENGINES IN- CLUDING INLET CONDITKGN BIAS DURING STEADY STATE OPERATION Andrew Kuzmitz, South Bend, Ind., assignor to The Bend ix Corporation, a corporation of Delaware Continuation of application Ser. No. 413,318, Mar. 1, 1954. This application July 5, 1957, Ser. No. 670,347 3 Claims. (Cl. 6039.28)

This invention relates to a fuel feed and power control device for gas turbine engines and more particularly to such a device utilizing an adjustable engine speed governor having throttle assist means and various speed setting compensatlng means operably connected thereto. This appllcation is a continuation of my parent application Serial No. 413,318, filed March 1, 1954, and now abandoned.

In the copending application of Barry C. Zeisloft, Serial lilo. 248,402, filed September 26, 1951 (common assignee), there is disclosed a fuel scheduling type control for turbo-prop and turbo-jet engines with which a pilot is free to accelerate to a selected power setting, and the quantity or weight of fuel supplied to the burners is automatically regulated to permit maximum allowable rate of acceleration within a safe turbine temperature limit and to avoid compressor surge or stall. This fuel control generally comprises an engine speed governor which is adapted to control the area of a Variable fuel metering orifice across which a fixed metering head is maintained. Superimposed on the governing action are scheduled limitations on fuel flow which provide turbine temperature and compressor surge protection during engine acceleration; deceleration fuel flow limitations; and controlled fuel flow for part load engine operation. All of these scheduled limitations of fuel fiow, with the exception of the deceleration flow schedule, are functions of a temperature corrected three dimensional cam system which controls the area of the metering orifice as a function of various engine operating conditions, such as engine speed and compressor discharge pressure.

The present invention is primarily concerned with improved means for adjusting the engine governor to control engine operation at any given selected speed, and with means for automatically resetting the governor as a function of certain engine operating conditions at a given selected steady state engine operating condition so that the engine may operate at maximum power or thrust at said steady state condition irrespective of variations in compressor inlet temperature and/or pressure. My invention, as herein disclosed, is associated with a single spool, i.e. a single compressor-turbine combination, turbojet engine, but, as will become apparent, is readily adaptable for use with a multiple spool, i.e. a multiple compressor-turbine combination, turbo-jet engine, with turboprop engines, or, for that matter, with any type of engine wherein governor resetting means, as hereinafter described, are utilizable for optimizing engine efficiency at certain operating conditions.

In many aircraft installations utilizing gas turbine engines, it has been found desirable to maintain turbine inlet temperature at a fixed maximum allowable value whenever the engine is controlled to operate at maximum steady state speed and power. However, the operating characteristics of many such engines vary if a fixed maximum speed is maintained, in such a way that turbine inlet temperature increases as compressor inlet temperature and/or pressure-decrease. I have found that by automatically resetting the engine speed governor as a predetermined function of compressor inlet temperature and compressor inlet pressure, during high power operation at a pilot selected maximum speed setting, for example, turbine inlet temperature may be controlled to a 3,Z,%ii Patented June '11, 1963 substantially constant value irrespective of variations in altitude temperature and/ or pressure.

In addition, the operating characteristics, as reflected in turbine inlet temperature and/ or percent of power output, of many such engines will normally vary at any given part throttle position of the pilots control lever, i.e. at any position between idle and maximum speed, with variations in altitude and/or compressor inlet temperature. My invention provides means for maintaining a substantially constant turbine inlet temperature or a substantially constant percent of engine power output, whichever is desired, at any given part throttle setting irrespective of variations in altitude and/or compressor inlet temperature. r

Furthermore, as will become later apparentib those skilled in the art, my invention is readily adaptable for use with multiple spool engines wherein it may be desirable to control the turbine temperature or percent of power output as a function of the speed setting on any one of the spools; egg. in a twin spool engine the engine governor may be automatically reset during engine operation as a function of the temperature and/or pressure conditions existent at the inlet of the second or high pressure compressor to control the percent of power output or turbine inlet temperature at any given pilots control lever position.

It is therefore one of the primary objects of this invention to provide automatic governor adjustment means for engines of the type specified operable to control the speed setting of said governor in such a manner that a predetermined turbine temperature or percent of power output is maintainable at steady state conditions and at any given position of a pilots control lever irrespective of variations in engine operating conditions.

Another object of this invention is to provide governor control means for automatically resetting an engine governor as a function of certain engine operating parameters whereby the governor speed setting may he auto matically varied at any given position of a pilots control lever.

It is a further object of this invention to provide gas turbine engine governing means automatically resettable during operation of the engine as a function of variations in pressure and/or temperature conditions at the inlet of a single spool engine or at the inlet of any one of the compressors of a multiple spool engine.

A further object of this invention is to provide all-speed governing means for gas turbine engines automatically resettable during operation of the engine as a function of a sensed compressor temperature and/or pressure for maintaining a predetermined maximum constant turbine inlet temperature irrespective of variations in altitude and/ or compressor inlet temperature.

An additional object of this invention is to provide manually actuable speed selection means for gas turbine engines including a throttle assist or power boost device for minimizing the force or torque necessary to manually select various engine operating speeds.

Another object of this invention is to provide maximum speed adjustment means for engines of the type specified operable to vary the maximum engine speed setting as desired without disturbing the idle speed setting thereof.

The above and other objects and features of this invention will become apparent from the following description of the device taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a sectional view of a turbojet engine equipped with a fuel feed and power control device in accordance with the invention;

FIGURE 2 is a schematic sectional view of the fuel feed and power control device used on the engine of FIGURE 1; and

FIGURES 3 and 4 are curve charts illustrating certain modes of operation of the engine of FIGURE 1 when equipped with the control device of FIGURE 2.

Referring now to FIGURE 1, a gas turbine engine is generally indicated at 10 and includes a series ofv annularly disposed combustion chambers 11 mounted in a casing having a header section 12, and a compressor 13, shown as of the axial flow type, which is driven by means ofa turbine 14 through a shaft 15. Each of the combustion chambers is provided with a burner nozzle 16 to which metered fuel is supplied under pressure by Way of a conduit '17, fuel manifold 18 and individual fuel lines 19. The conduit 17 receives metered fuel from a fuel control device generally indicated at 20 in FIGURE 1 and shown in sectional schematic in FIGURE 2 which will now be described.

The mechanism of the fuel control device 2% is enclosed within a housing 22 which provides for the passage of pressurized fuel through an inlet conduit 24, supplied by a pump, not shown, and for the passage of metered fuel to the conduit 17, manifold 18 and nozzles 16 through a discharge conduit 26. A reciprocable and rotatable main metering valve 28 having ribbed guide lands 28 and 28" is contained within a hollow valve sleeve member 30 and includes a hollow metering element 32 which defines a plurality of discriminately positioned metering openings 3-2. Fuel may flow from conduit 24 to conduit 26 through ports 34 in sleeve 30, metering restrictions 32', a chamber 36 and sleeveports 38. A pressure regulator valve device 40 is connected to conduits 24 and 26 by passages 42 and 44- and is adapted to by-pass fuel from conduit 24 to the pump inlet through a conduit 46, as necessary to maintain a constant fuel pressure difierential across metering valve element 32 under all conditions of engine opera tion. 'A valve stem 48, having a guide land 49, is connected to the valve guide land 28' and extends through an extension guide t) of sleeve member 30', being fixedly connected at its opposite end to a spring retainer 52 of an all-speed engine governing means 54.,

Governing means 54 comprises a speed reference means in the form of a governer spring 56 maintained between the movable retainer 52 and aspring adjustment member 57 which is axially actuable along guide 59 by a bifurcated lever 58 pivoted at 68 and connected to member 57 by means of lugs 62 which extend outwardly from the shell of said member. A pair of centrifugal weights 64 are in continuous abutment with spring retainer 52 at 66 and are pivoted at 68 on lugs 71} which are connected to a rotatable plate 72, said plate being drivably connected to the engine shaft 15 by means of geared member 74, gear 76 and governor drive shaft 78 (see FIGURE 1).

A pilot or manually controlled lever 80 is operatively connected to engine governor 24-, and more particularly to governor spring'56, by means of a lever 84 pivoted at 86 and arranged to rotate a contoured three-dimensional throttle or governor setting cam 88 through a rack and pinion 90, 92, said pinion 92 being telescoped on shafts 94 and 96 and being independently rotatable of said shafts and connected to cam 88 at 98, a cam follower 109, a cam follower lever 102 pivoted at 164, a servo control lever 106 pivoted at 108, a travel type servo device llt? including a fluid pressure controlling half-ball serve valve 112 selectively positionable by levers 8-0 and 166 and a fuel pressure actuated servo motor member 114, and a maximum speed adjustment member 116 pivoted at 117 and in continuous contact with member 114 at 1-18 and with'lever 58 at 120. The member 116, the pivot point 117 and, hence, the efiective lever arm acting on lever 58 are adjustable by means of athreaded member 121 which extends through the wall of housing 22.

The servo device 119 functions to minimize the throttle efiort necessary to compress governor spring 56 through the operative connection from lever 80 to saidspring and includes, in addition to servo valve 112 and servo motor member 1 14, a sleeve and spring retainer member 122 forming, with member 114, an expansible fluid pressure chamber 124 which is supplied with fuel under pressure from the fuel inlet conduit 24 through a passage 126, a constant discharge pressure valve 128 which maintains a constant predetermined servo supply pressure in a passage 130 and a calibrated restriction 132. Fuel is discharged by servo device 110 at a pressure determined by the position of half-ball servo valve 112 into a housing cavity 134 through a calibrated restriction 136 formed in the end of a tube 138 which is fixedly attached to sleeve 112-2 and forms a passage 14%. The housing cavity 13-4 is connected to the inlet side of the pump through a conduit, not shown. A spring 142 is anchored to sleeve 122 and abuts a slidable member 144 to which is connected -a cage-like member 146 which holds servo valve 112 in fixed relation to the one end of member 144. The servo fuel pressure in chamber 124, at any given constant supply pressure in passjage lSil, will vary only as a function of the area ratio of restrictions 132 and 136, the effective area of said latter restriction being a function of the position of servo valve 112 which is directly controlled by lever 80*, throttle setting cam 88 and levers 162 and .106. The spring 142 functions through levers 1116 and 1%2 to maintain cam follower 160 in continuous contact with cam 88 and a second cam follower 148 in continuous contact with a contoured three-dimensional compressor inlet pressure compensating cam 150 which is mounted on a pinion 152 and the shaft 94, said latter cam, pinion and shaft being loosely mounted on the shaft 96 which, in operation, is rotated as a function of engine speed by servo-mechanism, not shown, and which is drivably connected to a contoured three-dimensional acceleration cam 154 and nondrivably associated with cams 8S and 150.

A pressure responsive bellows 155 is shown mounted within chamber 134 and is internally vented to compressor inlet air through a conduit 155'. An evacuated bellows 155 is connected to bellows 155 by link 156 for nullifying any effect that variations in chamber 134 pressure would otherwise have on bellows 155. The bellows 155 is connected to a rack 157 'for actuating said rack, pinion 152 and cam 150 as a function of compressor inlet pressure, by means of a known type of servo device 158, including a fluid pressure actuated spring loaded piston 158' connected'to said rack, and a half-ball type servo valve 158" positionally controlled by bellows 155 through a lever 159 for controlling the effective area of an orifice 159 with relation to a fixed restriction 160 in a branch conduit 166' of servo supply passage 13!). A variation in compressor inlet pressure results in a corresponding variation in the extension of bellows 155; the operation of servo device 158 is suchthat earn 150 is rotated to an angular position which is always a function of existing compressor inlet pressure. Abutting the end of pinion 152 is the bifurcated end of a lever 1'62 pivoted at 164- and actuable in a clockwise direction with increases in compressor inlet temperature by a liquid filled temperature responsive bellows 166 connected to one end of'said lever and to a temperature probe 168 by a tube 17 t A fuel temperature compensated bellows arrangement, such as disclosed and claimed in the copending application Serial No. 222,001 of George Widell, filed April 20, -1 (common assignee), is preferred to the simple bellows 166.

Shaft 96 is stepped at 172 and, shaft 94 is maintained in abutting relation to a shank of pinion 92 at '174. It

should be understood that with the disclosed arrangetion, it should be noted that each of the cams is rotatableindependently of each of the other cams; i.e. shaft 96 rotates acceleration cam 154 as a predetermined function of engine speed but in no way affects the position of cam Each of 88 or cam 150; throttle setting cam 88 may be independently rotated along a different contour for each compressor inlet temperature to reset engine governor 54 by levers 80, 84 and rack and pinion 90, 92; and cam 150 is rotatable independently of each of earns 88 and 154 as a result of a change in length of pressure responsive bellows 155, said cam 150 being contoured to compensate the setting of governor 54 with changes in compressor inlet pressure at any given compressor inlet temperature, as will be more fully hereinafter explained.

A lever 176, pivoted at 178 and spring loaded by a tension spring 180 which maintains a cam follower 182 in continuous contact with the contoured surface of acceleration cam 154, has a lug 184 at one end thereof which is continuously positioned as a function of the contour of cam 154 for a purpose which will be hereinafter explained.

Fixedly connected to land 28" of metering valve 28 is an internally threaded member 186 from one side of which extends a lug 188 and into which is threaded a rod 190 having a flanged section 192 at the one end thereof which is movable between a minimum or deceleration stop 194 and lug 184 of acceleration control lever 176. The angular position of a rotatable shaft 196 is controlled to vary as a function of compressor discharge pressure by means of servo-mechanism, not shown, which is supplied with fuel from conduit 130. Servo-mechanism which may be readily adapted to rotate shaft 196 as a function of compressor discharge pressure and shaft 96 as a function of engine speed is disclosed and claimed in the copending application of Harry C. Zeisloft, supra. A bevel gear 198 on one end of shaft 196 is in mesh with a gear sector 200 of an annular element 202 which is telescoped within sleeve 30 and which defines a slot 294 in registry with lug 188. Lug 188 may move up and down in slot 204 with metering valve 28. Whenever a change in compressor discharge pressure occurs, as during acceleration, deceleration or steady state running of the engine at varying altitudes, gear 198 rotates element 202 thereby causing engagement of one or the other sides of slot 264 with lug 188 to rotate metering valve 28 in sleeve 36. The metering openings 32 in valve element 32 are so positioned that as valve 28 is rotated with an increase in compressor discharge pressure, an increasing number of metering openings come into registry with ports 34 to increase the fuel flow to the engine burners as a function of discharge pressure, whereas rotation of valve 28 in the opposite direction with decreasing discharge pressure has a reverse effect. In addition, Whenever metering valve 28 is actuated downwardly so as to accelerate the engine to a new selected speed, flange 192 contacts lug 184 of the acceleration lever 176 and the axial, as distinguished from the rotational, position of valve 28 becomes a function of engine speed and compressor inlet temperature as contoured into acceleration cam 154 until such time as centrifugal weights 64 develop sufiicient force at the new selected speed to overcome governor spring 56 and actuate valve 28 in a closing direction, whereby the engine is governed to said new selected speed.

During an engine deceleration, on the other hand, stem 190 is actuated against deceleration stop 194 and valve 28 assumes a fixed axial position while decreasing compressor discharge pressure functions to rotate said valve in a closing direction.

An idle speed adjustment lever is shown at 206, said lever being pivoted at 208 and connected at 210 to an extension of an idle adjustment screw 212. At any given position of adjustment screw 212 the position of lever 206 is fixed, the one end thereof functioning as a stop for lever 106 and servo valve 112 and thereby determining a maximum effective area of restriction 136 at said given adjustment of screw 212. All parts of the control 26 are illustrated in the approximate relations which they would assume if the engine were being operated at idle speed and at any given condition of compressor inlet temperature (T and compressor inlet pressure (P In this condition of operation, pilots lever is in a relatively retracted position and governor setting cam 88 is rotated to a position of relatively low cam rise, thereby permitting spring 142 to actuate servo valve 112 and lever 166 into contact with idle stop lever 206. A relatively low fuel pressure now exists in chamber 124 as a result of a relatively large area ratio between restriction 136 and restriction 132, which pressure acting on the face of servo motor member 114 is balanced by the force output of governor spring 56 acting through setting member 57, lever 58 and maximum speed adjustment member 116. The thereby selected degree of extension of governor spring 56 results in a force output opposing the force output of centrifugal weight 64, which forces reach equilibrium at idle speed, at which speed valve 28 is positioned as shown.

It has been found desirable in the operation of gas turbine engines that a given engine idle speed setting be maintained invariable at all times. It has also been found desirable to provide maximum speed adjustment means so that the maximum operating speed of any given engine may be varied, within limits as desired by a fuel control adjustment. Heretofore, an adjusted variation in maximum operating speed has resulted in an undesired variation in idle speed. The combined arrangement of the idle adjustment means 206, 212, the maximum speed adjustment means 116, and a secondary idle' adjustment thread 213 on retainer 52 avoids this deficiency. It is apparent that as member 116 is adjusted leftwardly the maximum operating speed will be decreased as a result of the decreasing distance between abutment point 126 and pivot 117 which results in a somewhat lesser degree of compression of governor spring 56 at maximum speed. Irrespective of variations in the adjusted position of member 116, however, the idle speed adjustment will not be varied inasmuch as lever 206 is always adjusted to axially align member 116 with its screw adjustment member and pivot 117 at an idle setting of the control. The upper collar of retainer 52 may then be adjusted as desired on thread 213 to vary the idle setting of spring 56 without affecting the setting of member 116. With this arrangement it is possible therefore, to vary adjusted maximum speed without affecting the idle speed adjustment and vice versa. The effect of this arrangement is illustrated in the curve chart of FIGURE 3, wherein governor spring compression is plotted against pilots lever angle. As illustrated, maximum spring compression (or engine speed) may be adjustably decreased by actuating member 116 leftwardly, and such adjustment has no effect whatever on the idle setting, as shown by curves 226', 222 and 224.

Referring now to the curve chart of FIGURE 4, the effect of variations in compressor inlet temperature (T and/or pressure (P on turbine inlet temperature at a constant 100 percent engine speed and at a variable maximum operating speed is illustrated. To obtain maximum steady state power from a gas turbine engine it is, of course, desirable to operate at maximum allowable turbine inlet temperature. If such an engine is operated at a constant 100 percent speed irrespective of variations in compressor inlet temperature, however, maximum allowable turbine inlet temperature Will be exceeded throughout the greater part of the range of variation of compressor inlet temperature, as illustrated by the vertical distance between curve 226 and curve 228. If a constant maximum adjusted speed is to be maintained Without exceeding maximum allowable turbine temperature at all con ditions of T and P a turbine temperature variation will be encountered with variations in T as illustrated by the constant percent maximum speed curve 230. From this curve it is apparent that an increasing amount of available thrust is lost with increasing compressor inlet temperature, and that the engine operates at the desired maximum allowable turbine temperature only when com pressor. inlet temperature decreases to about minus 90 F. To avoid this undesirable condition, I have contoured governor setting cam 88 in such a manner that at a power position of throttle lever 60 the selected percentage of maximum allowable engine speed will vary from about 92 per'cer'it't'o '100 percent as cam 88, along with cams 150 and 154, is actuated leftwardly by temperature responsive bellows 166 and lever 162 with compressor inlet temperature increasing from, say, minus 90 F. to plus 200 F. Such a control of engine speed setting with changes in compressor inlet temperature results in a variation in turbine inlet temperature from the desired maximum be tween minus 90 F. and plus 60 F, as illustrated by curve 232. In other words, under certain conditions of engine operation T, compensation alone has an 'overcompensating effect on engine speed and therefore turbine inlet temperature, particularly in the lower T, and P,

range.

lit has been further found that the variation of turbine inlet temperature along curve 232 will vary somewhat with wide variations in'altitude or compressor inlet pressure. 'In order, therefore to substantially meet the desired maximum turbine temperature throughout the range of illustrated compressor inlet temperatures, as shown by curve 228, I provide the 'cam 150 which may be contoured around its periphery at any given compressor inlet temperature below plus 60 F. to vary the maximum speed setting of governor 54 as bellows 155, acting through servo device 158 and rack and pinion 157, 152

' rotates said cam with variations in altitude, thereby causing cam follower 148 to follow said peripheral contour. With such an arrangement, that portion of curve 232 which lies between the illustrated minus 90 F. point and the plus 60 F. point may be caused to coincide with curve 228. The desired result of maintaining maximum allowable turbine inlet temperature at maximum or take oil power operation irrespective of variations in engine operating conditions is therefore obtained by varying the maximum speed setting of governor 94 as a predetermined function of compressor inlet temperature and/ or pressure.

It is apparent that earns 88 and 150 may also be contoured for substantially maintaining any given desired turbine temperature or constant percent of maximum power at part throttle operation. The maximum or 100 percent power point of operation was chosen for detailed discussion because the problem is most acute at this condition where it is mandatory that maximum allowable turbine inlet temperature be not exceeded. If in any given installation it is found that operation at part throttle need not be controlled with respect to maintenance of a given percent of maximum power or a given turbine inlet temperature, cam 88 need be contoured in two dimensions only instead of three, as shown.

Obviously, all of the foregoing recited specific values of temperatures and speed percentages are illustrative only and may be varied as desired to meet the various operat ing requirements of different engines by contouring came 88 and 150 as required.

'It is also apparent that temperature and pressure responsive bellows 166 and 155 may be sensitive to the temperature or pressure existent within any given stage !of a compressor and that the functional relation between a temperature and pressure sensed, say, in the fifth stage of a compressor and the temperature and pressure existent at the inlet of the compressor may be taken care of by proper contouring of cams 88 andiStl. In twin spool gas turbine engines where it may be desirable to control the speed of the high pressure compresscr-turbine combination, bellows 155 and 166 may be responsive to the pressure and temperature, respectively, at the inlet to the high pressure compressor.

In operation, if the pilot desired to quickly accelerate cam 88 through pinion 92 to a position of maximum cam rise at the existing compressor inlet temperature, thereby resulting in a counterclockwise rotation of lever 102 about follower 143 and a clockwise rotation of lever 106 about pivot 108 to move servo valve 112 in a closing direction with respect to restriction 136. As the eifective area of restriction 136 is thereby greatly reduced, the fuel pressure in chamber 124 increases a substantial amount and actuates servo motor member 114, speed adjustment member 116, lever 58 and spring retainer 57 downwardly to compress governor spring 56 to the selected speed setting. Compression of spring 56 results in an inward movement of centrifugal weights 64 and would actuate metering valve 28 to a wide open position but for the interference of acceleration cam and lever 154 and 176. An immediate increase in fuel flow results through valve element 32 to the engine burners which initiates acceleration of the engine. As the engine accelerates, shaft 96 rotates. acceleration cam 154 in proportion to existing engine speed, the contour of which cam is such as to control the rate of opening movement of valve 28 so that accelerating fuel flow is'metered to the burners to meet the maximum turbine inlet temperature and/ or compressor surge or stall limitations of the engine at any given compressor inlet temperature. In addition, as the engine accelerates shaft 196 is rotated as a function of compressor discharge pressure to rotate valve 28 in a fuel increasing direction.

As engine speed approaches maximum the centrifugal force generated by weights 64 begins to overcome spring 56 and move valve 28 in a closing direction and flange 92 oii of acceleration lever lug 184, whereby the engine is governed to said speed. If, at said maximum speed, the engine is taken to a high altitude, compressor inlet temperature and pressure responsive bellows 166 and 155, respectively, will actuate setting earns 88 and in such a manner that servo valve 112 will slightly increase the eifective area of restriction 136 resulting in a required lower maximum speed setting of governor 54 to maintain maximum turbine temperature at said lower maximum speed, as hereinbefore explained.

Although only one specific embodiment of my invention has been included in the description it will be understood that many variations may be made without departing from the scope of the invention.

I claim:

1. An engine speed governor comprising a flyweight device producing a force variable with instantaneous values of engine speed and a speed reference device including a throttle, a cam contoured for both axial and rotational movement movable in one of said directions by said throttle, and a governor spring producing a force opposing said fiyweight force, a servomechanism interposed between said throttle and said governor springincluding a hydraulically actuable servo motor member operably connected to said governor spring, a hydraulic pressure chamber formed on one side of said member, a servo valve for controlling the efiective pressure in said chamber, said servo valve being controlled by said cam for varying the hydraulic pressure in said chamber, means responsive to an engine operating temperature for actuating said cam in the other of said directions and independently of said throttle to vary the force of said governor spring means for fixing the'idle speed setting of said governor spring irrespective of theadjusted position of;

said throttle, means for adjusting the maximum selectable speed setting of said governor spring including a spring retainer for said governor spring, lever means for transferring the force from said throttle to said spring retainer, and means for adjusting said lever meanssuch that the effective lever arm acting on said spring retainer is varied to effect a corresponding variation in the maximum speed setting of said governor spring and at idle speed there is no effective change in said lever arm.

2. In a fuel feed and power control system for a .gas

turbine engine having a burner, a fuel conduit for conducting fuel to the burner, engine speed governing means including spring means for controlling fuel flow through Said conduit, manually controlled means for adjusting said spring means to select an operating speed for the engine, means for fixing the idle speed setting of said spring means irrespective of the adjusted position of said manual means, means for adjusting the maximum selectable speed setting of said spring means including a spring retainer for said spring means, lever means for transferring the force from said manually controlled means to said spring retainer, and means for adjusting said lever means such that the eflective lever arm acting on said spring retainer is varied to eifect a corresponding variation in the maximum speed setting of said spring means and at idle speed there is no eflective change in said lever arm.

3. In a fuel and power control system for a gas turbine engine having a burner, a fuel conduit for conducting fuel to the burner, engine speed governing means including spring means for controlling fuel flow through said conduit, manually controlled means for adjusting said spring means to select an operating speed for the engine, means for fixing the idle speed setting of said spring means irrespective of the adjusted position of said manual means, means for adjusting the maximum speed setting of said spring means including lever means for transferring the force from said manually controlled means to said spring means, and means for adjusting said lever means such that the eifective lever arm acting on said spring means is varied to effect a corresponding variation in the maximum speed setting of said spring means and at idle speed there is no eifective change in said lever arm.

References Cited in the file of this patent UNITED STATES PATENTS 2,422,808 Stokes June 24, 1947 2,536,158 Chamberlin Ian. 2, 1951 2,545,856 O-rr Mar. 20, 1951 2,720,751 Kunz Oct. 18, 1955 2,720,752 Chandler Oct. 18, 1955 2,750,734 Anxionnaz et al. June 19, 1956 2,759,549 Best Aug. 21, 1956 2,782,769 Best Feb. 6, 1957 2,846,846 Mock Aug. 12, 1958 2,857,739 Wright Oct. 28, 1958 3,032,986 Wright May 8, 1962 

1. AN ENGINE SPEED GOVERNOR COMPRISING A FLYWEIGHT DEVICE PRODUCING A FORCE VARIABLE WITH INSTANTANEOUS VALUES OF ENGINE SPEED AND A SPEED REFERENCE DEVICE INCLUDING A THROTTLE, A CAM CONTOURED FOR BOTH AXIAL AND ROTATIONAL MOVEMENT MOVABLE IN ONE OF SAID DIRECTIONS BY SAID THROTTLE, AND A GOVERNOR SPRING PRODUCING A FORCE OPPOSING SAID FLYWEIGHT FORCE, A SERVO-MECHANISM INTERPOSED BETWEEN SAID THROTTLE AND SAID GOVERNOR SPRING INCLUDING A HYDRAULICALLY ACTUABLE SERVO MOTOR MEMBER OPERABLY CONNECTED TO SAID GOVERNOR SPRING, A HYDRAULIC PRESSURE CHAMBER FORMED ON ONE SIDE OF SAID MEMBER, A SERVO VALVE FOR CONTROLLING THE EFFECTIVE PRESSURE IN SAID CHAMBER, SAID SERVO VALVE BEING CONTROLLED BY SAID CAM FOR VARYING THE HYDRAULIC PRESSURE IN SAID CHAMBER, MEANS RESPONSIVE TO AN ENGINE OPERATING TEMPERATURE FOR ACTUATING SAID CAM IN THE OTHER OF SAID DIRECTIONS AND INDEPENDENTLY OF SAID THROTTLE TO VARY THE FORCE OF SAID GOVER- 